The Mapping Lookup tool helps to ensure that your syntax is correct and that you are targeting the correct field for mapping by defining every part of the hierarchical Field Mapping path. 

Configure an Element's Mapping tab

1. Select the magnifying glass next to a Field Mapping input. Always start with the Object you are running the Form from. The following example assumes this Object is a Work Order.

  1. Type out 'Work Order' in the field path input. 
  2. Select Work Order

2. Type a dot '.'  after Work Order and type out the name of the Related Object/Details field name of Work Order. In this example the name is of a Custom Related Object.

The '__r' after Service Parts indicates that Service Parts is a Custom Object. 

3. If referencing a Related Object, type out another dot and search for and select the field name you want to display and then select Insert. Otherwise, select Insert after you have selected the relevant field name. 

The Mapping path has been generated and formatted with correct syntax. 

4. Save your changes.